Scratch
Easy
45 mins
235 points
What you need:
  • Computer/laptop

Make a Clock

In this lesson we program the hour, minute and second hands on a clock to point in the right direction and tell the time.

1 - Create a new Scratch project

Go to the Scratch website, create a new project and delete the cat sprite.

2 - Upload the clock face

Included with this step is a picture of a clock face. Save this picture to your computer and then upload it as a new sprite in your Scratch project.

Add the following code to the clock sprite to make it appear exactly in the center of the stage area.

when green flag clicked go to x (0) y (0)


3 - Draw the seconds hand

Now let's create the seconds hand of the clock by painting a new sprite.

Use the line tool to draw a blue line that is 4 pixels thick. Start the line from the center where the little gray circle and cross is. Hold down the 'Shift' key while you are drawing it to draw a straight line.

It is very important that you start it from the center, otherwise it will not line up correctly on the clock.

Once you have drawn the seconds hand, add the following code to it so that it appears correctly on the clock face.

when green flag clicked go to x (0) y (0)

Click the green flag and check that it appears correctly on the clock face. If it is too long or too small you may need to edit it so that it is the right size.




4 - Program the seconds hand

As you know the seconds hand of a clock counts the 60 seconds of each minute by rotating in one full circle.

If there are 360 degrees in one full rotation, the seconds hand will need to move 6 degrees each second as 6 X 60 = 360.

In the sensing toolbox there is a current [second] block, this block works like a variable and it is automatically set to the amount of seconds of the current time. By multiplying the current second by 6, we will get what degrees to point the seconds hand to.

Add the following code to the seconds hand sprite underneath the go to x: 0 y: 0 block.

when green flag clicked go to x (0) y (0) // add the new code under here forever point in direction ((current [second v]) * (6)) end

Once you have added the code, click on the green flag and the seconds hand should start rotating and point to each second.



5 - Draw the minutes hand

Now let's create the minutes hand of the clock by painting a new sprite.

Use the line tool to draw a red line that is 8 pixels thick. Start the line from the center where the little gray circle and cross is. Hold down the 'Shift' key while you are drawing it to draw a straight line. The minutes hand should be shorter than the seconds hand.

Again it is very important that you start it from the center, otherwise it will not line up correctly on the clock.

Once you have drawn the minutes hand, add the following code to it so that it appears correctly on the clock face.

when green flag clicked go to x (0) y (0)

Click the green flag and check that it appears correctly on the clock face. If it is too long or too small you may need to edit it so that it is the right size.



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This lesson is copyright of Coding Ireland. Unauthorised use, copying or distribution is not allowed.

Scratch is developed by the Lifelong Kindergarten Group at the MIT Media Lab. It is available for free at https://scratch.mit.edu
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